I had weapons grade irritability for many years when I first got ME/CFS, and looked into various possible causes and treatments in
this post. At that point in time I was just fumbling around in the dark biochemically, trying to find something that would help, but without much success.
Once I started on very low-dose amisulpride, nearly all of my irritability disappeared.
Abilify is also indicated as a treatment for the severe irritability that can arise in autism, so strange that it should cause irritability in some ME/CFS patients.
N-acetyl-cysteine sometimes helps irritability in autism, so that may be worth experimenting with.
Given that Abilify hits multiple serotonin receptors, that might be the cause of the irritability, since serotonin deficiency is linked to irritability. So something like an SSRI might help.